Methods and network node for activation of connection configuration for a secondary base station

ABSTRACT

The disclosure relates to a method (100) performed in a wireless device (1500) for handling connectivity to two network nodes (1, 2). The method (100) comprises receiving (101), from a first network node (1), a radio resource configuration message, the radio resource configuration message indicating a change in configuration of a connection towards a second network node (2); applying (102) the change in configuration towards the second network node (2) in response to the radio resource configuration message; and initiating (103) a random access procedure towards the second network node (2) after applying the change in configuration. The disclosure relates to corresponding wireless device, and to methods in network nodes, network nodes, computer programs and computer program products.

TECHNICAL FIELD

The present disclosure is directed to wireless communications and, moreparticularly, to addressing connectivity issues in wirelesscommunications networks that support simultaneous connections of awireless device to two base stations.

BACKGROUND

In a typical cellular radio system, wireless terminals (also referred toas user equipment unit nodes, UEs, mobile terminals, and/or mobilestations) communicate via a radio access network (RAN) with one or morecore networks, which provide access to data networks, such as theInternet, and/or the public-switched telecommunications network (PSTN).The RAN covers a geographical area that is divided into cell areas, witheach cell area being served by a radio base station (also referred to asa base station, a RAN node, a “NodeB”, and/or enhanced NodeB “eNodeB”).A cell area is a geographical area where radio coverage is provided bythe base station equipment at a base station site. The base stationscommunicate through radio communication channels with wireless terminalswithin range of the base stations.

Cellular communications system operators have begun offering mobilebroadband data services based on, for example, WCDMA (Wideband CodeDivision Multiple Access), HSPA (High Speed Packet Access), and LongTerm Evolution (LTE) wireless technologies. Moreover, fuelled byintroduction of new devices designed for data applications, end userperformance requirements are steadily increasing. The increased adoptionof mobile broadband has resulted in significant growth in traffichandled by high-speed wireless data networks. Accordingly, techniquesthat allow cellular operators to manage networks more efficiently aredesired.

Techniques to improve downlink performance may include 4-branch MIMO,multiflow communication, multi carrier deployment, etc. Since spectralefficiencies per link may be approaching theoretical limits, next stepsmay include improving spectral efficiencies per unit area. Furtherefficiencies for wireless networks may be achieved, for example, bychanging a topology of traditional networks to provide increaseduniformity of user experiences throughout a cell. Currently, so-calledheterogeneous networks are being developed for 3GPP as discussed, forexample, in: RP-121436, Study on UMTS Heterogeneous Networks, TSG RANMeeting #57, Chicago, USA, 4-7 Sep. 2012; R1-124512, Initialconsiderations on Heterogeneous Networks for UMTS, Ericsson,ST-Ericsson, 3GOO TSG RAN WG1 Meeting #70bis, San Diego, Calif., USA,8-12 Oct. 2012; and R1-124513, Heterogeneous Network DeploymentScenarios, Ericsson, ST-Ericsson, 3GPP TSG-RAN WG1 #70bis, San Diego,Calif., USA, 8-12 Oct. 2012.

A homogeneous network is a network of base stations (also referred to asNodeB's, enhanced NodeB's, or eNBs) in a planned layout, providingcommunications services for a collection of user terminals (alsoreferred to as user equipment nodes, UEs, and/or wireless terminals) inwhich all base stations may have similar transmit power levels, antennapatterns, receiver noise floors, and/or backhaul connectivity to thedata network. Moreover, all base stations in a homogeneous network mayoffer unrestricted access to user terminals in the network, and eachbase station may serve roughly a same number of user terminals. Currentcellular wireless communications systems in this category may include,for example, GSM (Global System for Mobile communication), WCDMA, HSDPA(High Speed Downlink Packet Access), LTE (Long Term Evolution), Wimax(Worldwide Interoperability for Microwave Access), etc.

In a heterogeneous network, low power base stations (also referred to aslow power nodes, LPNs, micro nodes, pico nodes, femto nodes, relaynodes, remote radio unit nodes, RRU nodes, small cells, RRUs, etc.) maybe deployed along with or as an overlay to planned and/or regularlyplaced macro base stations. A macro base station MBS may thus provideservice over a relatively large macro cell area and each LPN may provideservice for a respective relatively small LPN cell area within therelatively large macro cell area. Power transmitted by an LPN (e.g., 2Watts) may be relatively small compared to power transmitted by a macrobase station (e.g., 40 Watts for a typical macro base station). An LPNmay be deployed, for example, to reduce/eliminate a coverage hole(s) inthe coverage provided by the macro base stations, and/or to off-loadtraffic from macro base stations (e.g., to increase capacity in a hightraffic location, also referred to as a hot-spot). Due to the lowertransmit power and smaller physical size, an LPN may offer greaterflexibility for site acquisition.

SUMMARY

In initial discussions among members of the 3rd-Generation PartnershipProject (3GPP) regarding the development of Release 12 specificationsfor LTE, one of the proposed items for study is the possibility ofsimultaneously serving a User Equipment (UE) from more than one eNB. Inthe disclosure that follows, this is called “dual connectivity.” Thecontrol plane procedures of LTE have to be updated in order to supportthis.

With dual connectivity, activation of a new configuration mightencounter difficulties. For example, a UE may be connected to a mastereNB (MeNB) and add connectivity to a secondary eNB when given theopportunity, e.g. when being within coverage of a LPN providing the UE acapacity boosting by means of an additional radio resources. With two(or more) such connections, the UE may keep the control signalingconnection only with the MeNB, and only the master eNB (MeNB) then knowswhen a reconfiguration towards the SeNB has been applied by the UE. TheMeNB needs to inform the SeNB that the UE has applied thereconfiguration. However, meanwhile the UE may continue to communicateusing the radio resources of the SeNB. The configuration for thiscommunication can be old or new, which is not known by the SeNB. Onepossibility would be to indicate an activation time, as used in e.g.3G/HSPA, upon which the configuration is to be applied. However, such anactivation time must be set conservatively to ensure that the UE willreceive the configuration before activation, and thus this increases thedelay of radio resource reconfiguration.

An object of the present disclosure is to solve or at least alleviate atleast one of the above mentioned problems.

The object is according to a first aspect achieved by a method performedin a wireless device for handling connectivity to two network nodes. Themethod comprises: receiving, from a first network node, a radio resourceconfiguration message, the radio resource configuration messageindicating a change in configuration of a connection towards a secondnetwork node; applying the change in configuration towards the secondnetwork node in response to the radio resource configuration message;and initiating a random access procedure towards the second network nodeafter applying the change in configuration.

The method enables changing a connection configuration towards thesecond network node in a dual connectivity setup. The method ensuresthat the second network node and the wireless device change to the newconfiguration at the same time, and provides a delay efficient way forreconfiguration. By initiating the random access procedure towards thesecond network node, upon having executed the reconfiguration, thesecond network node is made aware of the fact that the wireless devicehas received and applied the new configuration, i.e. that the wirelessdevice has changed to the new configuration.

The object is according to a second aspect achieved by a wireless devicefor handling connectivity to two network nodes. The wireless device isconfigured to: receive, from a first network node, a radio resourceconfiguration message, the radio resource configuration messageindicating a change in configuration of a connection towards a secondnetwork node; apply the change in configuration towards the secondnetwork node in response to the radio resource configuration message,and initiate a random access procedure towards the second network nodeafter applying the change in configuration.

The object is according to a third aspect achieved by a computer programfor a wireless device for handling connectivity to two network nodes.The computer program comprises computer program code, which, whenexecuted on at least one processor on the wireless device causes thewireless device to perform the method of the first aspect above.

The object is according to a fourth aspect achieved by a computerprogram product comprising a computer program as above and a computerreadable means on which the computer program is stored.

The object is according to a fifth aspect achieved by a method performedin a first network node, for managing connectivity of a wireless deviceto the first network node and a second network node. The methodcomprises receiving, from the second network node, radio resourceconfiguration information for a connection between the wireless deviceand the second network node; sending in response to and based on theradio resource configuration information received from the secondnetwork node, a radio resource configuration message to the wirelessdevice, the radio resource configuration message indicating a change inconfiguration of a connection towards the second network node; andreceiving a message from the wireless device, the message indicatingthat the change in configuration is complete.

The object is according to a sixth aspect achieved by a first networknode for managing connectivity of a wireless device to the first networknode and a second network node. The first network node is configured to:receive, from the second network node, radio resource configurationinformation for a connection between the wireless device and the secondnetwork node; send in response to and based on the radio resourceconfiguration information received from the second network node, a radioresource configuration message to the wireless device, the radioresource configuration message indicating a change in configuration of aconnection towards the second network node; and receive a message fromthe wireless device, the message indicating that the change inconfiguration is complete.

The object is according to a seventh aspect achieved by a computerprogram for a first network node for managing connectivity of a wirelessdevice to the first network node and a second network node. The computerprogram comprises computer program code, which, when executed on atleast one processor on the first network node causes the first networknode to perform the method according to the fifth aspect above.

The object is according to an eight aspect achieved by a computerprogram product comprising a computer program as above, and a computerreadable means on which the computer program is stored.

The object is according to a ninth aspect achieved by a method performedin a second network node, for managing connectivity of a wireless deviceto a first network node and the second network node. The methodcomprises sending, to the first network node, radio resourceconfiguration information for a connection between the wireless deviceand the second network node; receiving a random access preamble from thewireless device, responsive to the radio resource configurationinformation; and sending a random access response to the wirelessdevice.

The object is according to a tenth aspect achieved by a second networknode for managing connectivity of a wireless device to a first networknode and the second network node. The second network node is configuredto: send, to the first network node, radio resource configurationinformation for a connection between the wireless device and the secondnetwork node; receive a random access preamble from the wireless device,responsive to the radio resource configuration information; and send arandom access response to the wireless device.

The object is according to an eleventh aspect achieved by a computerprogram for a second network node for managing connectivity of awireless device to a first network node and the second network node. Thecomputer program comprises computer program code, which, when executedon at least one processor on the second network node causes the secondnetwork node to perform the method according to the ninth aspect above.

The object is according to a twelfth aspect achieved by a computerprogram product comprising a computer program as above, and a computerreadable means on which the computer program is stored.

Further aspects, features and advantages of the present disclosure willbecome clear upon reading the following description and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic/block diagram illustrating the overall E-UTRANarchitecture.

FIG. 2 is a block diagram illustrating a functional split betweenE-UTRAN and the Evolved Packet Core (EPC).

FIG. 3 is a schematic diagram illustrating a user plane protocol stack.

FIG. 4 is a schematic diagram illustrating a control plane protocolstack.

FIG. 5 is a block diagram illustrating user plane and control plane dataflows.

FIG. 6 is a schematic diagram illustrating a heterogeneous deploymentwith a higher-power macro node and a lower-power pico node according tosome embodiments.

FIG. 7 is a schematic diagram illustrating an example heterogeneousdeployment where the pico node corresponds to a cell of its own (a “picocell”). The indices “p” and “m” indicate common signals/channels for thepico and macro cell respectively.

FIG. 8 is a schematic diagram illustrating an example heterogeneousdeployment where the pico node does not correspond to a cell of its own.

FIG. 9 is a schematic diagram illustrating single-frequency network(SFN) operation with identical transmission from macro and pico nodes toa wireless terminal according to some embodiments.

FIG. 10 is a schematic diagram illustrating dual connectivity operationwith the UE (wireless terminal) having multiple connections with boththe master (macro) and secondary (pico) nodes according to someembodiments.

FIG. 11 is a block diagram illustrating a protocol architecture formultiple connectivity according to some embodiments.

FIG. 12 is a signal flow diagram illustrating a contention-based randomaccess procedure in LTE.

FIG. 13 is a schematic diagram illustrating control plane terminationfor dual connectivity, according to some embodiments.

FIG. 14 is a signal flow diagram illustrating an example procedure forparameter negotiation between a master eNB and a secondary eNB.

FIG. 15 is a signal flow diagram illustrating an example procedure forconfiguring a mobile terminal connection towards a secondary eNB.

FIG. 16 is a process flow diagram illustrating steps of an exampletechnique from a mobile terminal perspective.

FIG. 17 is a signal flow diagram illustrating an example procedure forchanging configuration of the connection between a mobile terminal and asecondary eN.

FIG. 18 is a signal flow diagram illustrating another example procedurefor for configuring a mobile terminal connection towards a secondaryeNB.

FIG. 19 is a block diagram illustrating elements of an example mobileterminal, according to some embodiments.

FIG. 20 is a block diagram illustrating elements of an example wirelessnetwork node, according to some embodiments.

FIG. 21 illustrates schematically an environment in which embodiments ofthe present disclosure may be implemented.

FIG. 22 is a flow chart over steps of a method in a wireless device inaccordance with an aspect of the present disclosure.

FIG. 23 illustrates a wireless device comprising functionmodules/software modules for implementing embodiments of the presentdisclosure.

FIG. 24 is a flow chart over steps of a method in a first network nodein accordance with an aspect of the present disclosure.

FIG. 25 illustrates a first network node comprising functionmodules/software modules for implementing embodiments of the presentdisclosure.

FIG. 26 is a flow chart over steps of a method in a second network nodein accordance with an aspect of the present disclosure.

FIG. 27 illustrates a second network node comprising functionmodules/software modules for implementing embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Inventive concepts will now be described more fully hereinafter withreference to the accompanying drawings, in which examples of embodimentsof inventive concepts are shown. Inventive concepts may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of present inventive concepts to those skilled inthe art. It should also be noted that these embodiments are not mutuallyexclusive. Components from one embodiment may be tacitly assumed to bepresent or used in another embodiment.

For purposes of illustration and explanation only, these and otherembodiments of present inventive concepts are described herein in thecontext of operating in a Radio Access Network (RAN) that communicatesover radio communication channels with wireless terminals (also referredto as UEs). It will be understood, however, that present inventiveconcepts are not limited to such embodiments and may be embodiedgenerally in any type of communication network. As used herein, awireless terminal or UE can include any device that receives data from acommunication network, and may include, but is not limited to, a mobiletelephone (“cellular” telephone), laptop/portable computer, pocketcomputer, hand-held computer, desktop computer, a machine to machine(M2M) or MTC type device, a sensor with a wireless communicationinterface, etc.

In the following, aspects are described for facilitating thoroughunderstanding of the context of the present disclosure.

In some embodiments of a RAN, several base stations may be connected(e.g., by landlines or radio channels) to a radio network controller(RNC). A radio network controller, also sometimes termed a base stationcontroller (BSC), may supervise and coordinate various activities of theplural base stations connected thereto. A radio network controller maybe connected to one or more core networks. According to some otherembodiments of a RAN, base stations may be connected to one or more corenetworks without a separate RNC(s) therebetween, for example, withfunctionality of an RNC implemented at base stations and/or corenetworks.

The Universal Mobile Telecommunications System (UMTS) is a thirdgeneration mobile communication system, which evolved from the GlobalSystem for Mobile Communications (GSM), and is intended to provideimproved mobile communication services based on Wideband Code DivisionMultiple Access (WCDMA) technology. UTRAN, short for UMTS TerrestrialRadio Access Network, is a collective term for the Node B's and RadioNetwork Controllers which make up the UMTS radio access network. Thus,UTRAN is essentially a radio access network using wideband code divisionmultiple access for UEs.

The Third Generation Partnership Project (3GPP) has undertaken tofurther evolve the UTRAN and GSM based radio access networktechnologies. In this regard, specifications for the Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) are ongoing within 3GPP. TheEvolved Universal Terrestrial Radio Access Network (E-UTRAN) comprisesthe Long Term Evolution (LTE) and System Architecture Evolution (SAE).

Note that although terminology from WCDMA and/or HSPA is used in thisdisclosure to exemplify embodiments of the inventive concepts, thisshould not be seen as limiting the scope of inventive concepts to onlythese systems. Other wireless systems, including 3GPP (3rd GenerationPartnership Project) LTE (Long Term Evolution), WiMax (WorldwideInteroperability for Microwave Access), UMB (Ultra Mobile Broadband),HSDPA (High-Speed Downlink Packet Access), GSM (Global System for MobileCommunications), etc., may also benefit from exploiting embodiments ofpresent inventive concepts disclosed herein.

Also note that terminology such as base station (also referred to asNodeB, eNodeB, or Evolved Node B) and wireless terminal (also referredto as User Equipment node or UE) should be considering non-limiting anddoes not imply a certain hierarchical relation between the two. Ingeneral, a base station (e.g., a “NodeB” or “eNodeB”) and a wirelessterminal (e.g., a “UE”) may be considered as examples of respectivedifferent communications devices that communicate with each other over awireless radio channel. While embodiments discussed herein may focus onwireless transmissions in a downlink from a NodeB to a UE, embodimentsof inventive concepts may also be applied, for example, in an uplink.Furthermore, although the description below focuses, for purposes ofillustration, on example embodiments in which described solutions areapplied in heterogeneous networks that include a mix of relativelyhigher-power (e.g., “macro”) base stations and relatively lower-powernode (e.g., “pico”) base stations, the described techniques may beapplied in any suitable type of network, including both homogeneous andheterogeneous configurations. Thus, the base stations involved in thedescribed configurations may be similar or identical to one another, ormay differ in terms of transmission power, number oftransmitter-receiver antennas, processing power, receiver andtransmitter characteristics, and/or any other functional or physicalcapability.

With the proliferation of user friendly smart phones and tablets, theusage of high data rate services such as video streaming over the mobilenetwork is becoming commonplace, greatly increasing the amount oftraffic in mobile networks. Thus, there is a great urgency in the mobilenetwork community to ensure that the capacity of mobile networks keepsup increasing with this ever-increasing user demand. The latest systemssuch as Long Term Evolution (LTE), especially when coupled withinterference mitigation techniques, have spectral efficiencies veryclose to the theoretical Shannon limit. The continuous upgrading ofcurrent networks to support the latest technologies and densifying thenumber of base stations per unit area are two of the most widely usedapproaches to meet the increasing traffic demands.

Yet another approach that is gaining high attention is to useHeterogeneous Networks where the traditional pre-planned macro basestations (known as the macro layer) are complemented with severallow-powered base stations that may be deployed in a relatively unplannedmanner. The 3rd Generation Partnership Project (3GPP) has incorporatedthe concept of Heterogeneous Networks as one of the core items of studyin the latest enhancements of LTE, such as LTE release 11, and severallow-powered base stations to realize heterogeneous networks such as picobase stations, femto base stations (also known as home base stations orHeNBs), relays, and RRHs (remote radio heads) have been defined.

Initial discussions for LTE release 12 have begun, and one of theproposed items for study is the possibility of serving a User Equipmentnode (also referred to as a UE, a wireless terminal, etc.) from morethan one eNB (also referred to as a base station) simultaneously. Thecurrent legacy handover mechanisms of LTE may have to be updated tosupport this.

The Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) includesbase stations called enhanced NodeBs (eNBs or eNodeBs), providing theE-UTRA user plane and control plane protocol terminations towards theUE. The eNBs are interconnected with each other using the X2 interface.The eNBs are also connected using the S1 interface to the EPC (EvolvedPacket Core), more specifically to the MME (Mobility Management Entity)by means of the S1-MME interface and to the Serving Gateway (S-GW) bymeans of the S1-U interface. The S1 interface supports many-to-manyrelation between MMEs/S-GWs and eNBs. The E-UTRAN architecture isillustrated in FIG. 1.

The eNB hosts functionalities such as Radio Resource Management (RRM),radio bearer control, admission control, header compression of userplane data towards serving gateway, and/or routing of user plane datatowards the serving gateway. The MME is the control node that processesthe signaling between the UE and the CN (core network). Significantfunctions of the MME are related to connection management and bearermanagement, which are handled via Non Access Stratum (NAS) protocols.The S-GW is the anchor point for UE mobility, and also includes otherfunctionalities such as temporary DL (down link) data buffering whilethe UE is being paged, packet routing and forwarding to the right eNB,and/or gathering of information for charging and lawful interception.The PDN Gateway (P-GW) is the node responsible for UE IP addressallocation, as well as Quality of Service (QoS) enforcement (as furtherdiscussed below).

FIG. 2 illustrates a summary of functionalities of the different nodes,and the reader is referred to 3GPP TS 36.300 v11.5.0 and the referencestherein for further details of functionalities of the different nodes.In FIG. 2, blocks eNB, MMe, S-GW, and P-GW illustrate logical nodes;blocks Inter Cell RRM, RB Control, Connection Mobility Cont., RadioAdmission Control, eNB Measurement Configuration & Provision, DynamicResource Allocation (Scheduler), NAS Security, Idle State MobilityHandling, EPS bearer Control, Mobility Anchoring, UE IP addressallocation, and Packet Filtering illustrate functional entities of thecontrol plane; and blocks RRC, PDCP, RLC, MAC, and PHY illustrate theradio protocol layers.

The radio protocol architecture of E-UTRAN is divided into the userplane and the control plane. FIG. 3 illustrates the protocol stack forthe user-plane. The user plane protocol stack includes the Packet DataConvergence Protocol (PDCP), Radio Link Control (RLC), and Medium AccessControl (MAC), which are terminated at the eNB. The PDCP manages IPpackets in the user plane and it performs functionalities such as headercompression, security, and re-ordering and retransmission duringhandover. The RLC layer is mainly responsible for segmentation (andcorresponding assembly) of PDCP packets, so that they fit the size thatis actually to be transmitted over the air interface. RLC can operateeither in unacknowledged mode or acknowledged mode, where the lattersupports retransmissions. The MAC layer performs multiplexing of datafrom different radio bearers, and it is the one that informs the RLCabout the size of the packets to provide, which is decided based on therequired QoS (Quality of Service) of each radio bearer and the currentcapacity available to the UE.

FIG. 4 illustrates the control plane protocol stack. The layers belowthe Radio Resource Control (RRC) layer perform the same functionality asin the user plane, except that there is no header compression in thecontrol plane. The main functions of the RRC are the broadcasting ofsystem information, RRC connection control (establishment, modification,and release of RRC connection, establishment of signaling radio bearers(SRB) and data radio bearers (DRBs), handover, configuration of lowerprotocol layers, radio link failure recovery, etc.), and measurementconfiguration and reporting. Details of the RRC protocol functionalitiesand procedures can be found in 3GPP TS 36.331 v11.3.0.

A UE is uniquely identified over the S1 interface within an eNB with theeNB UE S1AP ID. When an MME receives an eNB UE S1AP ID, the MME storesit for the duration of the UE-associated logical S1-connection for thisUE. Once known to an MME, this IE (information element) is included inall UE-associated S1-AP signaling. The eNB UE S1AP ID is unique withinthe eNB, and a UE is assigned a new S1AP ID after a handover by thetarget eNB.

From the MME side, a UE is uniquely identified using the MME UE S1AP ID.When an eNB receives MME UE S1AP ID, the eNB stores it for the durationof the UE-associated logical S1 connection for this UE. Once known to aneNB, this IE is included in all UE-associated S1-AP signaling. The MMEUE S1AP ID is unique within the MME, and it is changed if the UE's MMEchanges (for example, handover between two eNBs connected to differentMMEs).

The flow of user plane and control plane data is illustrated in FIG. 5.There is only one MAC entity per UE (unless the UE supports multiplecarriers in the case of carrier aggregation), and under this MAC entityseveral Hybrid ARQ (HARQ) processes might be running simultaneously, forrapid retransmissions. There is a separate RLC entity for each radiobearer and if the radio bearer is configured to use PDCP, there is alsoone separate PDCP entity for that bearer. A bearer is configured to usePDCP only if it is dedicated to a UE. In other words, multicast andbroadcast data do not utilize PDCP both in the control and user plane,and the PDCP is used only for dedicated control message in the controlplane and for dedicated UL/DL data in the user plane.

At the transmitting side, each layer receives a Service Data Unit (SDU)from a higher layer, and sends a Protocol Data Unit (PDU) to the lowerlayer. For example, PDCP PDUs are sent towards the RLC, and they are RLCSDUs from RLC point of view, which in turn sends RLC PDUs towards theMAC, which are MAC SDUs from the MAC point of view. At the receivingend, the process is reversed (i.e., each layer passing SDUs to the layerabove it, where they are perceived as PDUs).

A UE can have multiple applications running at the same time, eachhaving different QoS (Quality of Service) requirements (for example,VoIP, browsing, file download, etc.). To support these differentrequirements, different bearers are set up, each being associated with arespective QoS. An EPS bearer/E-RAB (Radio Access Bearer) is the levelof granularity for bearer level QoS control in the EPC/E-UTRAN. That is,Service Data Flows (SDF) mapped to the same EPS bearer receive the samebearer level packet forwarding treatment (e.g. scheduling policy, queuemanagement policy, rate shaping policy, RLC configuration, etc.).

One EPS bearer/E-RAB is established when the UE connects to a PDN(Packet Data Network), and that remains established throughout thelifetime of the PDN connection to provide the UE with always-on IPconnectivity to that PDN. That bearer is referred to as the defaultbearer. Any additional EPS bearer/E-RAB that is established to the samePDN is referred to as a dedicated bearer. The initial bearer level QoSparameter values of the default bearer are assigned by the network,based on subscription data. The decision to establish or modify adedicated bearer can only be taken by the EPC, and the bearer level QoSparameter values are always assigned by the EPC.

The packets of an EPS bearer are transported over a radio bearer betweenthe UE and eNB. An S1 bearer transports the packets of an EPS bearerbetween the eNB and S-GW. An E-RAB is actually a concatenation of thesetwo bearers (i.e., radio bearer and S1 bearer), and the two bearers aremapped on a one to one fashion. An S5/S8 bearer transports the packetsof the EPS bearer between the S-GW and P-GW, and completes the EPSbearer. Here also there is a one to one mapping between the E-RAB andS5/S8 bearer.

Heterogeneous Networks and Dual/Multiple Connectivity

A heterogeneous deployment or heterogeneous network, as illustrated inFIG. 6, includes network transmission nodes (e.g., micro and pico nodesor base stations) operating with different transmit powers and withoverlapping coverage areas. A heterogeneous deployment/network isconsidered as an interesting deployment strategy for cellular networks.In such a deployment, the low-power nodes (“pico nodes”) are typicallyassumed to offer high data rates (Mbit/s) and/or to provideincreased/high capacity (users/m2 or Mbit/s/m2) in the local areas whereincreased data rates/capacity is/are needed/desired, while thehigh-power nodes (“macro nodes”) are assumed to provide full-areacoverage. In practice, the macro nodes may correspond to currentlydeployed macro cells while the pico nodes are later deployed nodes,provided to extend capacity and/or achievable data rates within themacro-cell coverage area where needed/desired. FIG. 6 illustrates aheterogeneous deployment with a higher-power macro node and alower-power pico node. In a typical case, there may be multiple piconodes within the coverage area of a macro node.

FIG. 7 illustrates heterogeneous deployment where the pico nodecorresponds to a cell of its own (a “pico cell”). The indices “p” and“m” indicate common signals/channels for the pico and macro cellrespectively. A pico node of a heterogeneous deployment may operate as acell of its own (a “pico cell”) as shown in FIG. 7. This means that, inaddition to downlink and uplink data transmission/reception, the piconode also transmits the full set of common signals/channels associatedwith a cell. In the LTE context this full set of common signals/channelsincludes:

-   -   The Primary and Secondary Synchronization Signals (PSS and SSS)        corresponding to the Physical Cell Identity of the pico cell.    -   The Cell-specific reference signals (CRS), also corresponding to        the Physical Cell Identity of the cell. The CRS can, for        example, be used for downlink channel estimation to enable        coherent demodulation of downlink transmissions.    -   The Broadcast channel (BCH), with corresponding pico-cell system        information. Additional system information may also be        transmitted on the PDSCH physical channel.

As the pico node transmits the common signals/channels, thecorresponding pico cell can be detected and selected (connected to) by aterminal (UE, user equipment).

If the pico node corresponds to a cell of its own, also so-called L1/L2control signaling on the Physical Downlink Control Channel of PDCCH (aswell as Physical Control Format Indicator Channel or PCFICH and PhysicalHybrid-ARQ Indicator Channel or PHICH) are transmitted from the piconode to connected terminals, in addition to downlink data transmissionon the Physical Downlink Shared Channel or PDSCH. The L1/L2 controlsignaling, for example, provides downlink and uplink schedulinginformation and Hybrid-ARQ-related information to terminals within thecell. This is shown in FIG. 7.

FIG. 7 illustrates a heterogeneous deployment where the pico nodecorresponds to a cell of its own (a “pico cell”). The indices “p” and“m” indicate common signals/channels for the pico and macro cellrespectively. As shown in FIG. 7, the pico node uses/transmits its ownprimary and secondary synchronization signals PSSp and SSSp, cellspecific reference signals CRSp, and broadcast channel BCHp that areindependent of (e.g., different than) the primary and secondarysynchronization signals PSSm and SSSm, cell specific reference signalsCRSm, and broadcast channel BCHm used/transmitted by the macro node.Accordingly, the UE may communicate through the pico node withoutsupport from the macro node.

Alternatively, a pico node within a heterogeneous deployment may notcorrespond to a separate cell of its own, but may instead provide adata-rate and/or capacity “extension” of the overlaid macro cell. Thisis sometimes known as “shared cell” or “soft cell”. In this case, atleast the CRS, PBCH (physical broadcast channel), PSS and SSS aretransmitted from the macro node (but not the pico node). The PDSCH(physical downlink shared channel) can be transmitted from the piconode. To allow for demodulation and detection of the PDSCH, despite thefact that no CRS is transmitted from the pico node, DM-RS (downlinkmodulation reference signal) may be transmitted from the pico nodetogether with the PDSCH. The UE-specific reference signals can then beused by the terminal for PDSCH demodulation/detection. This is shown inFIG. 8, which illustrates a heterogeneous deployment where the pico nodedoes not correspond to or define a cell of its own.

Transmitting data from a pico node not transmitting CRS as describedabove may require DM-RS support in/at the wireless terminal UE(“non-legacy terminal”). In LTE, DM-RS-based PDSCH reception issupported in Rel-10 and for FDD while for the L1/L2 control signaling,DM-RS-based reception is planned for Rel-11. For terminals notsupporting DM-RS-based reception (“legacy terminals”) one possibility ina shared cell setting is to exploit SFN-type (Single Frequency Networktype) of transmission. In essence identical copies of the signals andchannels necessary for a legacy terminal are transmitted simultaneouslyfrom the macro and pico nodes. From a terminal perspective, this willlook as a single transmission. Such an operation (i.e. SFN operationwith identical transmission from macro and pico to a terminal), which isillustrated in FIG. 9, may only provide an SINR gain, which can betranslated into a higher data rate but not a capacity improvement,because transmission resources cannot be reused across sites within thesame cell. As shown in FIG. 10, SFN operation may be provided withidentical transmissions from macro and pico to a wireless terminal UE.

Assume that the macro nodes are able to provide coverage and the piconodes are provided only for capacity enhancements (i.e., to reducecoverage holes), another alternative architecture is where the UEmaintains connectivity to the macro node, or, more generally, the“Master eNB” (MeNB), all the time, and adds connectivity to the piconode, or, more generally, the “Secondary eNB” (SeNB), when it is in thecoverage area of the pico node. The link between the UE and the MeNB maybe referred to as the “anchor” link, while the link between the UE andSeNB can be referred to as the “booster” link. When both connections areactive, the anchor link can be used for control signaling while thebooster link is used for data. In addition, it may also be possible tosend data via the anchor link. This is illustrated in FIG. 10, i.e. dualconnectivity operation with the UE having simultaneous activeconnections with both the master and secondary base stations. In thiscase, as in the previous cases, the system information is shown to besent only from the MeNB, but it is still possible to send it also fromthe SeNB. As shown in FIG. 10, in soft cell operation, the UE may havemultiple connections with both the anchor and booster nodes (alsoreferred to as the macro and pico nodes).

Protocol Architecture Dual Connectivity

The term “dual connectivity” is used to refer to operation where the UEconsumes radio resources provided by at least two different networkpoints connected with non-ideal backhaul. Furthermore, each eNB involvedin dual connectivity for a UE may assume different roles. Those roles donot necessarily depend on the eNB's power class and can vary among UEs.

To support multiple connectivity to micro and pico nodes, severalarchitectural options are possible both for the control and user planes.For the user plane, a centralized approach may be provided where thePDCP (or even the RLC) is terminated at the anchor node only and thebooster node terminates at the RLC (or even the MAC) level. Adecentralized approach may be to have the booster to terminate at thePDCP level. A similar approach can be taken in the control plane (i.e.,distributed or centralized PDCP/RLC) but on top of that the additionaldimension of centralizing or distributing the RRC may be provided.Figure ii shows example control and user plane architectures where theuser plane uses distributed PDCP, while the control plane is centralizedat the PDCP level at the anchor node. Note that in FIG. 11, user planeaggregation (i.e., the possibility to split the packets belonging to oneapplication data flow over the anchor and booster links) can be realizedby using a higher layer aggregation protocol like multi-path TCP(MPTCP).

Random access (RA) serves as an uplink control procedure to enable theUE to access the network. The RA procedures serve three main purposes:

-   -   The RA procedures let the UE align its uplink (UL) timing to        that expected by the eNodeB in order to minimize interfering        with other UEs transmissions. UL time alignment is a requirement        in E-UTRAN before data transmissions can commence.    -   The RA procedures provide a means for the UE to notify the        network of its presence and enable the eNodeB to give the UE        initial access to the system.    -   The RA procedures notify the eNB that the UE has data in its        uplink buffer.

In addition to its usage during initial access, the RA procedures arealso used when the UE has lost the uplink synchronization.

The basic RA Procedure is a four-phase procedure as outlined in FIG. 12,thus illustrating Contention based Random Access Procedure in LTE.

-   -   Phase 1 consists of transmission of a random access preamble by        the UE, allowing the Node B to estimate the transmission timing        of the UE. Uplink synchronization is necessary as the UE        otherwise cannot transmit any uplink data. The preamble used in        this step can be either randomly selected by the UE in        contention-based Random Access procedures, or dedicated by the        network in contention-free Random Access procedures. The latter        solution can be used in case of handover, for example, when the        target eNB may signal dedicated random access information to the        source eNB, which will further convey that information to the        UE.    -   Phase 2 consists of the network transmitting the Random Access        Response message. This message includes the timing advance        command to correct the uplink timing, based on the timing of        arrival measurement in the first step. In addition to        establishing uplink synchronization, the second step also        assigns uplink resources. In the case of contention based random        access, a temporary identifier to the UE is included, to be used        in the third step in the random access procedure.    -   Phase 3 consists of signalling from the UE to the eNB, also        called as Msg3. This step is included in contention-based Random        Access. A primary function of this message is to uniquely        identify the UE. The exact content of this signalling depends on        the state of the UE, e.g., whether it is previously known to the        network or not. In connected state, the UE includes at least its        C-RNTI in the Msg3.    -   Phase 4, the final phase, is responsible for contention        resolution to solve the potential case when in case multiple UEs        tried to access the system on the same resource. This phase is        used in contention-based Random Access procedure.

Phase 1—Random Access Preamble

The UE obtains information about which preambles are available (eitherto select one at random or to use a specified one), whether one orrepeated preambles should be used, what the desired received power levelshould be at the base station, what power increase step should be usedin case of failed preamble reception, what the maximum number of randomaccess preamble transmission is, when it is allowed to transmit thepreamble, etc.

If the UE obtains the Phase I information via dedicated signaling, suchas when random access is performed as part of handover (the dedicatedsignaling originated from the target cell, forwarded to the UE by theserving cell), a specific preamble may be configured. In addition, thetimer T304 is started with a value provided by the dedicated signaling.

The UE determines a random access resource for preamble transmission inconsideration of the retrieved information. Either, the information isrelated to the downlink synchronization of the serving cell, or relatedto a non-serving cell. The latter can be the case when random access isused to get established in a target cell during handover.

Phase 2—Random Access Response

The UE monitors PDCCH of the cell for random access response in the RAresponse window, which starts at the subframe that contains the end ofthe preamble transmission plus three subframes and has the lengthra-ResponseWindowSize.

If no response has been received, and the max number of preambletransmissions has been reached, or the timer T304 has expired, thehandover attempt is considered failed and higher layer is informed.Then, the UE initiates the RRC connection reestablishment procedure torestore the connection to the source cell, specifying thereestablishment cause to handover failure. Furthermore, a radio linkfailure report is prepared.

Control Plane Protocol Termination for Dual Connectivity

There are currently different options for control plane termination fordual connectivity. The option considered here is where the UE has onesingle RRC entity, which communicates with a single RRC entity locatedin the MeNB on the network side. This is shown in FIG. 13 (Control planetermination for dual connectivity). In this scenario, all controlsignaling between the UE and the network terminates in the MeNB. Onlythe MeNB generates the final RRC messages to be sent towards the UEafter coordination of RRM functions between MeNB and SeNB. The UE RRCentity sees all messages coming only from one entity (in the MeNB) andthe UE only replies back to that entity.

Note, that one option could foresee a “virtual RRC” entity in the SeNBthat generates parts of the RRC message to be finally sent to the UE bythe MeNB. This scheme is similar to the case of handover (HO), where thetarget eNB generates the RRC message to be sent to the UE by the sourceeNB. The difference between the dual-connectivity situation scenariopresented here and HO is that in the former scenario the MeNB may needto check the contents of the partial RRC message and assemble the finalRRC message.

In the following, it can be assumed that each node controls its ownradio resources. This is necessary, since an eNB acting as SeNB towardsone UE may at the same time act as MeNB towards another UE. In otherwords, MeNB and SeNB are UE-specific roles of an eNB. Thus, to ensureefficient usage of radio resources, each eNB must be in control of itsown radio resources and a distributed Radio Resource Management (RRM)needs to be assumed.

Negotiating Parameters between SeNB and MeNB

There is a need for a procedure between the MeNB and the SeNB to agreeon the UE radio resource configuration. For instance, a procedure isneeded to enable the setup, the modification or the handover of a UEbearer for which radio resources are provided by a radio network node(SeNB) that is different from the radio network node (MeNB) that hoststhe RRC connection and the connection to the core network. In addition,there might be a need to modify the physical or MAC layer RRCconfiguration used in the SeNB.

One important thing to consider here are the UE capabilities. The UEcapabilities indicate whether the UE supports some features (static),but also indicate what is the maximum amounts of certain radio resourcesthat can be allocated (dynamically) to the UE (e.g., number of ROHCcontext sessions).

FIG. 14 illustrates a procedure for parameter negotiation between MeNBand SeNB. The assumed procedure for negotiating radio resourceconfiguration of the connection between the UE and the SeNB is shown inFIG. 14, and involves the following steps:

1. MeNB provides current radio resource configurations and capabilitiesof the UE for the SeNB (over Xn). This may be done within the messagethat triggers the setup of resources within the SeNB.

2. The SeNB decides the radio resource configuration relevant for theSeNB and signals this to the MeNB (over Xn). This may be done inresponse to the message triggering the setup of resources within theSeNB or during triggering the modification of already establishedresources.

3. The MeNB either accepts the radio resource configuration relevant forthe SeNB, or rejects it and sends a NACK to the SeNB If the parameternegotiation function was triggered during setup/HO of resources towardsthe SeNB, there might not be the need for an explicit ACK. In case ofresource modification, if the radio resource configuration is acceptedby the MeNB, it replies ACK back to the SeNB. If not, a NACK is sent.

Benefits of this solution comprise:

-   -   the current model with SRB₁/SRB₂ is sufficient    -   It requires only one set of PDCP encryption keys for control        plane    -   One entity takes the final decision→no risk of exceeding        capabilities    -   No need for parallel procedures for the UE (current model        applies)

However, there is one issue with the single RRC entity solution, whichrelates to the reconfiguration of the connection between the UE and theSeNB. The SeNB does not know when the UE has received theRRCConnectionReconfiguration and applied it. This is shown in FIG. 15,i.e. configuration of UE connection towards SeNB.

Currently, according to Release 8 of the 3GPP specifications, the eNBcan know the exact time when the UE applies by RRC configuration only ifRRCConnectionReconfiguration is equipped with mobilityControlInfo andthe UE triggers Random Access when it applies the configuration.

With dual connectivity, activation of the new configuration might bemore problematic:

-   -   Only the MeNB knows when RRCReconfiguration has been applied        (based on L2 feedback+max. processing time or based on Random        Access)    -   The MeNB needs to inform the SeNB that it has received RA from        the UE. However, meanwhile the UE may continue to use radio        resources of the SeNB. The configuration for this communication        can be old or new, which is not known by the SeNB. One        possibility would be to indicate an activation time, as used in        e.g. 3G/HSPA. However, such an activation time must be set        conservatively to ensure the UE will receive the configuration        before activation, and thus this increases the delay of radio        resource reconfiguration. Thus it would be preferable to have a        solution without such an activation time.

Detailed below are mechanisms to overcome these problems related toconfiguration of the UE connection towards SeNB. Restated, the problemaddressed with these mechanisms is related to dual connectivity in LTERel-12. A connection between the UE and secondary eNB is setup by themaster eNB on the initiative of the secondary eNB. Radio resourceconfiguration of the secondary eNB can be also updated, in which casethe signaling can be performed by the master eNB based on input from thesecondary eNB. However, the secondary eNB does not know when the UE hasreceived the connection configuration info from the master eNB, andtherefore cannot know when to start communicating with the UE or whenthe UE has applied the new configuration. The embodiments describedbelow solve this problem.

In short, the solution according to some of these embodiments is to letthe UE perform a random access towards the SeNB, rather than towards theMeNB, to indicate that it has received and applied the newconfiguration. In this way, the SeNB will know that the UE has changedto the new configuration.

Examples of these general principles are shown in FIG. 16 and FIG. 17,which illustrate the main steps of an example technique from a mobileterminal perspective and a signal flow diagram illustrating the presenttechniques, respectively. FIG. 17 illustrates a procedure for changingconfiguration of the connection between UE and SeNB, and it is notedthat message names are given as examples.

In several embodiments, the method involves the following steps:

1. MeNB provides current radio resource configuration and capabilitiesof the UE to the SeNB (over Xn)

2. The SeNB decides the radio resource configuration relevant for theSeNB and signals this to the MeNB (over Xn) (compare arrow “Parameterchange request” of FIG. 17).

3. The MeNB accepts the radio resource configuration relevant for theSeNB, includes possible changes to the radio resource configurationrelevant to the MeNB and transmits this to the UE (compare arrow“RRCConnection reconfiguration” of FIG. 17). If changes are made, theseare communicated back to the SeNB.

4. The UE receives and decodes the configuration message and determinesthat it includes a change of the configuration of the connection towardsthe SeNB. This determination can be based on implicit or explicitinstruction in the configuration message.

i. The configuration message may include the Information Element (IE):MobilityControlInformation

ii. The configuration message may include a dedicated random accesspreamble to be used to acknowledge the configuration change towards theSeNB.

iii. The configuration message may also include a specific C-RNTI to beused in msg3 of the random access procedure

iv. The configuration may include a separate flag triggering a randomaccess procedure towards the SeNB.

5. The UE applies the new SeNB configuration

6. The UE performs (initiates) a random access procedure towards SeNB toindicate that is has taken the new configuration into use (compare arrow“Random access preamble” of FIG. 17).

i. The random access preamble can be a dedicated preamble, if providedby the network. By using a dedicated preamble, the SeNB will be able todetect that the random access is to accept the new UE configuration.However, due to the limited number of available preambles, this may notalways be a feasible solution.

ii. SeNB responds with random access response (compare arrow “Randomaccess response” of FIG. 17), including RA-RNTI and Time Alignment (TA)information.

iii. If the UE was not allocated with the dedicated preamble, the UEsends a Msg3 includes a C-RNTI for contention resolution (compare arrow“Msg3 (including SeNB allocated C-RNTI)” of FIG. 17). In thisdisclosure, the C-RNTI would be assigned by SeNB, and will identify theUE in the SeNB. In an alternative embodiment, The C-RNTI can also beconfigured by the MeNB. It can for example be configured separately whenthe SeNB connection is established, it could have been associated with aC-RNTI that is used by UE for acknowledging RRC updates towards SeNB

7. The UE completes the procedure by sending theRRCConnectionReconfigurationComplete message to the MeNB (compare arrow“RRC Connection Reconfiguration Complete” of FIG. 17).

8. The MeNB signals the parameter change ACK to the SeNB (compare arrow“Parameter change ACK” of FIG. 17).

It is noted that the order in which the UE performs (initiates) therandom access procedure towards the SeNB (under point 6 above) and sendsthe RRCConnectionReconfigurationComplete message to the MeNB (underpoint 7 above) may alternatively be the opposite (i.e. sendingRRCConnectionReconfigurationComplete message to the MeNB beforeperforming (initiates) the random access procedure towards the SeNB).

The random access procedure can be performed (initiated) differently indifferent embodiments. In one embodiment, the UE is allocated with oneC-RNTI for MeNB. Then when the UE is connected to the SeNB, a separateC-RNTI can be allocated. Finally, the UE can be allocated yet anotherspecific C-RNTI which is used only in the synchronization towards theSeNB as described below. By this way the SeNB can identify both the UEbut also that the UE has updated the RRC configuration.

In dual connectivity thus, two C-RNTIs may be independently allocated:one for the MeNB and one for SeNB.

In one embodiment, the UE establishes downlink synch with the SeNB andtransmits the RA preamble using a RA configuration to the SeNB, and willmonitoring a response from SeNB. One example is when the SeNB isoperating a cell on a different carrier than the MeNB, but it could alsobe the same.

In another embodiment, the UE maintains downlink synch with MeNB andtransmits the RA preamble using a RA configuration to the MeNB. The SeNBis configured to monitor RA resources associated to the MeNB and willdetect RA preambles transmitted using the MeNB configuration for RA.Thereby, the UE does not need to establish downlink synch with SeNB,which can be important for example when MeNB and SeNB are operating onthe same carrier. Also, the UE will be able to maintain communicationwith the MeNB rather than having to interrupt data channel communicationwith MeNB in order to perform (initiate) RA with SeNB.

In this embodiment the MeNB can provide extra details to the SeNB afterreceiving a Parameter Change Request (as per FIG. 17). This extrainformation concerns the RA procedure to be invoked between the UE andthe MENB and may consist of the RACH preamble, mask index andtime-frequency domain resources used by the UE to perform (initiate) theRA on the MeNB. An example of the messages involved in this procedure isshown in FIG. 18 (it is again noted that message names are given asexamples).

A procedure is thus provided for changing the SeNB connectionconfiguration in a dual connectivity setup. The procedure includes amethod for ensuring that SeNB and UE move to the new configuration atthe same time.

The advantage of this technique is that it provides a procedure for theSeNB to know exactly when the UE has applied the new configurationprovided by the SeNB, without the need for the SeNB to make anyassumptions or to unnecessarily wait for a certain pre-determined pointin time.

Hardware Implementations

Several of the techniques and methods described above may be implementedusing radio circuitry and electronic data processing circuitry providedin a terminal. FIG. 19 illustrates features of an example terminal 1500according to several embodiments of the present invention. Terminal1500, which may be a UE configured for dual-connectivity operation withan LTE network (E-UTRAN), for example, comprises a transceiver unit 1520for communicating with one or more base stations as well as a processingcircuit 1510 for processing the signals transmitted and received by thetransceiver unit 1520. Transceiver unit 1520 includes a transmitter 1525coupled to one or more transmit antennas 1528 and receiver 1530 coupledto one or more receiver antennas 1533. The same antenna(s) 1528 and 1533may be used for both transmission and reception. Receiver 1530 andtransmitter 1525 use known radio processing and signal processingcomponents and techniques, typically according to a particulartelecommunications standard such as the 3GPP standards for LTE. Notealso that transmitter unit 1520 may comprise separate radio and/orbaseband circuitry for each of two or more different types of radioaccess network, such as radio/baseband circuitry adapted for E-UTRANaccess and separate radio/baseband circuitry adapted for Wi-Fi access.The same applies to the antennas—while in some cases one or moreantennas may be used for accessing multiple types of networks, in othercases one or more antennas may be specifically adapted to a particularradio access network or networks. Because the various details andengineering tradeoffs associated with the design and implementation ofsuch circuitry are well known and are unnecessary to a fullunderstanding of the disclosure, additional details are not shown here.

Processing circuit 1510 comprises one or more processors 1540 coupled toone or more memory devices 1550 that make up a data storage memory 1555and a program storage memory 1560. Processor 1540, identified as CPU1540 in FIG. 19, may be a microprocessor, microcontroller, or digitalsignal processor, in some embodiments. More generally, processingcircuit 1510 may comprise a processor/firmware combination, orspecialized digital hardware, or a combination thereof. Memory 1550 maycomprise one or several types of memory such as read-only memory (ROM),random-access memory, cache memory, flash memory devices, opticalstorage devices, etc. Because terminal 1500 supports multiple radioaccess networks, processing circuit 1510 may include separate processingresources dedicated to one or several radio access technologies, in someembodiments. Again, because the various details and engineeringtradeoffs associated with the design of baseband processing circuitryfor mobile devices are well known and are unnecessary to a fullunderstanding of the disclosure, additional details are not shown here.

Typical functions of the processing circuit 1510 include modulation andcoding of transmitted signals and the demodulation and decoding ofreceived signals. In several embodiments of the present disclosure,processing circuit 1510 is adapted, using suitable program code (e.g. inthe form of a computer program 1570) stored in program storage memory1560, for example, to carry out one of the techniques described abovefor access network selection. Of course, it will be appreciated that notall of the steps of these techniques are necessarily performed in asingle microprocessor or even in a single module.

Similarly, several of the techniques and processes described above canbe implemented in a network node, such as an eNodeB or other node in a3GPP network. FIG. 20 is a schematic illustration of a node 1 in which amethod embodying any of the presently described network-based techniquescan be implemented. A computer program 50, 60 for controlling the node 1to carry out a method embodying the present invention is stored in aprogram storage 30, which comprises one or several memory devices. Dataused during the performance of a method embodying the present inventionis stored in a data storage 20, which also comprises one or more memorydevices. During performance of a method embodying the present invention,program steps are fetched from the program storage 30 and executed by aCentral Processing Unit (CPU) 10, retrieving data as required from thedata storage 20. Output information resulting from performance of amethod embodying the present invention can be stored back in the datastorage 20, or sent to an Input/Output (I/O) interface 40, whichincludes a network interface for sending and receiving data to and fromother network nodes and which may also include a radio transceiver forcommunicating with one or more terminals.

Accordingly, in various embodiments of the invention, processingcircuits, such as the CPU 10 and memory circuits 20 and 30 in FIG. 20,are configured to carry out one or more of the techniques described indetail above. Likewise, other embodiments may include radio networkcontrollers including one or more such processing circuits. In somecases, these processing circuits are configured with appropriate programcode, stored in one or more suitable memory devices, to implement one ormore of the techniques described herein. Of course, it will beappreciated that not all of the steps of these techniques arenecessarily performed in a single microprocessor or even in a singlemodule.

FIG. 21 illustrates schematically an environment in which embodiments ofthe present disclosure may be implemented. As described earlier, acommunication system may comprise a number of network nodes 1, 2providing wireless communication for wireless devices 1500. The networknodes 1, 2 may comprise base stations, e.g. eNBs communicating over awireless interface with the wireless devices 1500 and over a wiredconnection with each other.

FIG. 22 is a flow chart over steps of a method in a wireless device 1500in accordance with an aspect of the present disclosure. The method 100may be performed in the wireless device 1500 for handling connectivityto two network nodes 1, 2. The method 100 comprises receiving 101, froma first network node 1, a radio resource configuration message, theradio resource configuration message indicating a change inconfiguration of a connection towards a second network node 2.

The method 100 comprises applying 102 the change in configurationtowards the second network node 2 in response to the radio resourceconfiguration message.

The method 100 comprises initiating 103 a random access proceduretowards the second network node 2 after applying the change inconfiguration. Such initiating may comprise transmitting a random accesspreamble.

By initiating the random access procedure towards the second networknode 2, upon having executed the reconfiguration, the second networknode 2 is made aware of the fact that the wireless device 1500 hasreceived and applied the new configuration, i.e. that the wirelessdevice 1500 has changed to the new configuration (comprisingconnection(s) towards the second network node 2).

In an embodiment, the method 100 comprises sending 104 a message to thefirst network node 1, the message indicating that the change inconfiguration is completed.

In an embodiment, the method 100 comprises receiving, from the firstnetwork node 1, a message comprising information for initiating therandom access procedure towards the second network node 2.

In a variation of the above embodiment, the information comprises adedicated random access preamble and/or an identifier of the wirelessdevice 1500 such as Cell Radio Network Temporary Identifier, C-RNTI, forthe second network node 2.

In a variation of the above embodiment, the random access procedurecomprises a contention free random access and the initiating 103 therandom access procedure comprises:

-   -   establishing downlink synchronization towards the second network        node 2 and    -   transmitting the received information to the second network node        2.

In a variation of the above embodiment, the method 100 comprisesmonitoring a response from the second network node 2.

In various embodiments, the information for initiating the random accessprocedure towards the second network node is included in the radioresource configuration message.

In an embodiment, the random access procedure comprises a contentionbased random access and the initiating 103 the random access procedurecomprises:

-   -   transmitting a randomly selected random access preamble,    -   receiving a random access response comprising a random access        code, such as Random Access Radio Network Temporary Identifier,        RA-RNTI, from the second network node 2, and    -   transmitting, to the second network node 2, a message comprising        an identifier of the wireless device 1500, the identifier        comprising a Cell Radio Network Temporary Identifier, C-RNTI,        assigned by the second network node 2.

In a variation of the above embodiment, the method 100 comprisesreceiving, from the second network node 2 a contention resolutionmessage.

FIG. 19, described earlier, shows a wireless device 1500 which may beconfigured to perform the various embodiments of the method 100. Awireless device 1500 is thus, in an aspect, provided for handlingconnectivity to two network nodes 1, 2. The wireless device 1500 isconfigured to:

-   -   receive, from a first network node 1, a radio resource        configuration message, the radio resource configuration message        indicating a change in configuration of a connection towards a        second network node 2,    -   apply the change in configuration towards the second network        node 2 in response to the radio resource configuration message,        and    -   initiate a random access procedure towards the second network        node 2 after applying the change in configuration.

In an embodiment, the wireless device 1500 is configured to send amessage to the first network node 1, the message indicating that thechange in configuration is completed.

In an embodiment, the wireless device 1500 is configured to receive,from the first network node 1, a message comprising information forinitiating the random access procedure towards the second network node2.

In a variation of the above embodiment, the information comprises adedicated random access preamble and/or an identifier of the wirelessdevice 1500 such as Cell Radio Network Temporary Identifier, C-RNTI, forthe second network node 2.

In a variation of the above embodiment, the random access procedurecomprises a contention free random access and the wireless device 1500is configured to initiate the random access procedure by:

-   -   establishing downlink synchronization towards the second network        node 2 and    -   transmitting the received information to the second network node        2.

In a variation of the above embodiment, the wireless device 1500 isconfigured to monitor a response from the second network node 2.

In an embodiment, the information is included in the radio resourceconfiguration message.

In an embodiment, the random access procedure comprises a contentionbased random access and the wireless device 1500 is configured toinitiate the random access procedure by:

-   -   transmitting a randomly selected random access preamble,    -   receiving a random access response comprising a random access        code, such as Random Access Radio Network Temporary Identifier,        RA-RNTI, from the second network node 2, and    -   transmitting, to the second network node 2, a message comprising        an identifier of the wireless device 1500, the identifier        comprising a Cell Radio Network Temporary Identifier, C-RNTI,        assigned by the second network node 2.

In a variation of the above embodiment, the wireless device 1500 isconfigured to receive, from the second network node 2 a contentionresolution message.

The present disclosure also encompasses a computer program forimplementing the embodiments of the method as described above inrelation to FIG. 22. Such computer program 1570 may be used in awireless device 1500 for handling connectivity to two network nodes 1,2. The computer program 1570 comprises computer program code, which,when executed on at least one processor 1540 on the wireless device1500) causes the wireless device 1500 to perform the method 100 asdescribed in relation to FIG. 22.

The present disclosure also encompasses a computer program product 1560comprising a computer program 1570 as described above and a computerreadable means on which the computer program 1570 is stored. Asmentioned earlier (compare description relating to FIG. 19), suchcomputer program product 1560 may comprise (ROM), random-access memory,cache memory, flash memory devices, optical storage devices, etc.

An example of an implementation using function modules/software modulesis illustrated in FIG. 23, in particular illustrating a wireless device1500 comprising function modules and/or software modules forimplementing embodiments of the method 100. The wireless device 1500comprises first means, for example a first function module 111, forreceiving, from a first network node 1, a radio resource configurationmessage, the radio resource configuration message indicating a change inconfiguration of a connection towards a second network node 2. Suchmeans may comprise processing circuitry receiving signaling viareceiving circuitry and antenna(s) of the wireless device 1500 (referalso to description in relation to FIG. 19).

The wireless device 1500 comprises second means, for example a secondfunction module 112, for applying the change in configuration towardsthe second network node 2 in response to the radio resourceconfiguration message. Such means may comprise processing circuitry(refer also to description in relation to FIG. 19).

The wireless device 1500 comprises third means, for example a thirdfunction module 113, for initiating a random access procedure towardsthe second network node 2 after applying the change in configuration.Such means may comprise processing circuitry for transmitting signalingvia transmitting circuitry and antenna(s) of the wireless device 1500(refer also to description in relation to FIG. 19).

The wireless device 1500 may comprise yet additional means forperforming the various steps of the method. For example, the wirelessdevice 1500 may comprise a function module 114, for sending a message tothe first network node 1, the message indicating that the change inconfiguration is completed. Yet additional means for performing themethod may be included in the wireless device 1500.

The function modules/software modules 111, 112, 113, 114 can beimplemented using software instructions such as computer programexecuting in a processor and/or using hardware, such as applicationspecific integrated circuits, field programmable gate arrays, discretelogical components etc.

FIG. 24 is a flow chart over steps of a method in a first network nodein accordance with an aspect of the present disclosure. The method 200may be performed in a first network node 1, for managing connectivity ofa wireless device 1500 to the first network node 1 and a second networknode 2. The method 200 comprises:

-   -   receiving 201, from the second network node 2, radio resource        configuration information for a connection between the wireless        device 1500 and the second network node 2,    -   sending 202 in response to and based on the radio resource        configuration information received from the second network node        2, a radio resource configuration message to the wireless device        1500, the radio resource configuration message indicating a        change in configuration of a connection towards the second        network node 2, and    -   receiving 203 a message from the wireless device (1500), the        message indicating that the change in configuration is complete.

In an embodiment, the method 200 comprises sending a parameter changeacknowledgement to the second network node 2, in response to the messageindicating that the change in configuration is complete.

In an embodiment, the method 200 comprises, after the receiving 201 theradio resource configuration message, transmitting to the second networknode 2 information about a random access procedure to be invoked betweenthe wireless device 1500 and the first network node 1. By providing thesecond network node 2 information about the random access procedure, thesecond network node 2 is enabled to monitor the random access resourcesassociated with the first network node 1, and may detect e.g. RApreambles (if included in the information) transmitted during the randomaccess procedure between the wireless device 1500 and the first networknode 1.

FIG. 20, described earlier, shows a network node 1 which may beconfigured to perform the various embodiments of the method 200. A firstnetwork node 1 is thus, in an aspect, provided for managing connectivityof a wireless device 1500 to the first network node 1 and a secondnetwork node 2. The first network node 1 is configured to:

-   -   receive, from the second network node 2, radio resource        configuration information for a connection between the wireless        device 1500 and the second network node 2,    -   send in response to and based on the radio resource        configuration information received from the second network node        2, a radio resource configuration message to the wireless device        1500, the radio resource configuration message indicating a        change in configuration of a connection towards the second        network node 2, and    -   receive a message from the wireless device 1500, the message        indicating that the change in configuration is complete.

In an embodiment, the first network node 1 is configured to send aparameter change acknowledgement to the second network node 2, inresponse to the message indicating that the change in configuration iscomplete.

In an embodiment, the first network node 1 is configured to, after thereceiving 201 the radio resource configuration message, transmit to thesecond network node 2 information about a random access procedure to beinvoked between the wireless device 1500 and the first network node 1.The present disclosure also encompasses a computer program forimplementing the embodiments of the method as described e.g. above inrelation to FIG. 24. The computer program 50 (see FIG. 20) may be usedfor a first network node 1 for managing connectivity of a wirelessdevice 1500 to the first network node 1 and a second network node 2. Thecomputer program 1570 comprises computer program code, which, whenexecuted on at least one processor on the first network node 1 causesthe first network node 1 to perform the method 200 as described inrelation to FIG. 24.

The present disclosure also encompasses a computer program product 30comprising a computer program 50 as above, and a computer readable meanson which the computer program 50 is stored. As mentioned earlier(compare description relating to FIGS. 19 and 20), such computer programproduct 30 may comprise (ROM), random-access memory, cache memory, flashmemory devices, optical storage devices, etc.

An example of an implementation using function modules/software modulesis illustrated in FIG. 25, in particular illustrating a first networknode 1 comprising function modules and/or software modules forimplementing embodiments of the method 200. The first network node 1comprises first means, for example a first function module 211, forreceiving, from the second network node 2, radio resource configurationinformation for a connection between the wireless device 1500 and thesecond network node 2. Such means may comprise processing circuitry forreceiving signals via an interface (refer also to description inrelation to FIG. 20).

The first network node 1 comprises second means, for example a secondfunction module 212, for sending in response to and based on the radioresource configuration information received from the second network node2, a radio resource configuration message to the wireless device 1500,the radio resource configuration message indicating a change inconfiguration of a connection towards the second network node 2. Suchmeans may comprise processing circuitry for transmitting signals via aninterface (refer also to description in relation to FIG. 20).

The first network node 1 comprises third means, for example a thirdfunction module 213, for receiving a message from the wireless device1500, the message indicating that the change in configuration iscomplete. Such means may comprise processing circuitry for receivingsignals via an interface (refer also to description in relation to FIG.20).

The first network node 1 may comprise yet additional means forperforming the various steps of the method. For example, the firstnetwork node 1 may comprise a function module (not illustrated in FIG.25), sending a parameter change acknowledgement to the second networknode 2, in response to the message indicating that the change inconfiguration is complete. Yet additional means for performing themethod may be included in the first network node 1.

The function modules/software modules 211, 212, 213 can be implementedusing software instructions such as computer program executing in aprocessor and/or using hardware, such as application specific integratedcircuits, field programmable gate arrays, discrete logical componentsetc.

FIG. 26 is a flow chart over steps of a method in a second network nodein accordance with an aspect of the present disclosure. The method 300may be performed in a second network node 2, for managing connectivityof a wireless device 1500 to a first network node 1 and the secondnetwork node 2. The method 300 comprises:

-   -   sending 301, to the first network node 1, radio resource        configuration information for a connection between the wireless        device 1500 and the second network node 2,    -   receiving 302 a random access preamble from the wireless device        1500, responsive to the radio resource configuration        information, and    -   sending 303 a random access response to the wireless device        1500.

In an embodiment, the method 300 comprises receiving a parameter changeacknowledgement from the first network node 1.

In an embodiment, the sending 301 the radio resource configurationinformation comprises including a dedicated identifier for the wirelessdevice 1500, the dedicated identifier comprising a Cell Radio NetworkTemporary Identifier, C-RNTI, for the second network node 2.

In an embodiment, the receiving 302 comprises receiving the dedicatedidentifier comprising a Cell Radio Network Temporary Identifier, C-RNTI,for the second network node 2 for identifying the wireless device 1500.

FIG. 20, described earlier, shows a network node 2 which may beconfigured to perform the various embodiments of the method 300. Asecond network node 2 is thus, in an aspect, provided for managingconnectivity of a wireless device 1500 to a first network node 1 and thesecond network node 2. The second network node 2 is configured to:

-   -   send, to the first network node 1, radio resource configuration        information for a connection between the wireless device 1500        and the second network node 2,    -   receive a random access preamble from the wireless device 1500,        responsive to the radio resource configuration information, and    -   send a random access response to the wireless device 1500.

In an embodiment, the second network node 2 is configured to receive aparameter change acknowledgement from the first network node 1.

In an embodiment, the sending 301 the radio resource configurationinformation comprises including a dedicated identifier for the wirelessdevice 1500, the dedicated identifier comprising a Cell Radio NetworkTemporary Identifier, C-RNTI, for the second network node 2.

In an embodiment, the second network node 2 is configured to receive byreceiving the dedicated identifier comprising a Cell Radio NetworkTemporary Identifier, C-RNTI, for the second network node 2 foridentifying the wireless device 1500.

It is noted that the method 100 performed in a first network node,comprising e.g. a master eNB, and the method 200 performed in a secondnetwork node, comprising e.g. a secondary eNB, may both be implementedin one and the same network node. In particular, a network node,exemplified in the following by eNB, may be the master eNB for onewireless device while being the secondary eNB for another wirelessdevice, and the network node would thus benefit from being configured toperform both methods 100, 200.

The present disclosure also encompasses a computer program forimplementing the embodiments of the method as described e.g. above inrelation to FIG. 26. The computer program 60 (see FIG. 20) may be usedfor a second network node 2 for managing connectivity of a wirelessdevice 1500 to a first network node 1 and the second network node 2. Thecomputer program 60 comprises computer program code, which, whenexecuted on at least one processor on the second network node 2 causesthe second network node 2 to perform the method 300 as described withreference to FIG. 26.

The present disclosure also encompasses a computer program product 30comprising a computer program 60 as above, and a computer readable meanson which the computer program 60 is stored.

An example of an implementation using function modules/software modulesis illustrated in FIG. 27, in particular illustrating a second networknode 2 comprising function modules and/or software modules forimplementing embodiments of the method 300. The second network node 2comprises first means, for example a first function module 311, forsending, to the first network node 1, radio resource configurationinformation for a connection between the wireless device 1500 and thesecond network node 2. Such means may comprise processing circuitry forsending signals via an interface (refer also to description in relationto FIG. 20).

The second network node 2 comprises second means, for example a secondfunction module 312, for receive a random access preamble from thewireless device 1500, responsive to the radio resource configurationinformation. Such means may comprise processing circuitry for receivingsignals via an interface (refer also to description in relation to FIG.20).

The second network node 2 comprises third means, for example a thirdfunction module 313, for sending a random access response to thewireless device 1500. Such means may comprise processing circuitry forsending signals via an interface (refer also to description in relationto FIG. 20).

The second network node 2 may comprise yet additional means forperforming the various steps of the method. For example, the secondnetwork node 2 may comprise a function module (not illustrated in FIG.27), sending the radio resource configuration information comprisesincluding a dedicated identifier for the wireless device 1500, thededicated identifier comprising a Cell Radio Network TemporaryIdentifier, C-RNTI, for the second network node 2. Yet additional meansfor performing the method may be included in the second network node 2.

The function modules/software modules 311, 312, 313 can be implementedusing software instructions such as computer program executing in aprocessor and/or using hardware, such as application specific integratedcircuits, field programmable gate arrays, discrete logical componentsetc. It will be appreciated by the person of skill in the art thatvarious modifications may be made to the above described embodimentswithout departing from the scope of the present invention. For example,although embodiments of the present invention have been described withexamples that include a communication system compliant to the 3GPPspecified LTE standard specification, it should be noted that thesolutions presented may be equally well applicable to other networksthat support dual connectivity. The specific embodiments described aboveshould therefore be considered exemplary rather than limiting the scopeof the invention. Because it is not possible, of course, to describeevery conceivable combination of components or techniques, those skilledin the art will appreciate that the present invention can be implementedin other ways than those specifically set forth herein, withoutdeparting from essential characteristics of the invention. The presentembodiments are thus to be considered in all respects as illustrativeand not restrictive.

Embodiments of the inventive techniques and apparatus described aboveinclude, but are not limited to:

1. A method, in a mobile terminal, for handling connectivity to two basestations, the method comprising:

receiving, from a first base station, a radio resource configurationmessage, the radio resource configuration message indicating a change inconfiguration of a connection towards a second base station;

apply the change in configuration of the connection towards the secondbase station, in response to the radio resource configuration message;

performing a random access procedure towards the second base station,after applying the change in configuration;

sending a message to the first base station, the message indicating thatthe change in configuration is complete.

2. A method, in a first base station, for managing connectivity of amobile terminal to the first base station and a second base station, themethod comprising:

receiving, from the second base station, radio resource configurationinformation for a connection between the mobile terminal and the secondbase station;

in response to and based on the radio resource configuration informationreceived from the second base station, sending a radio resourceconfiguration message to the mobile terminal, the radio resourceconfiguration message indicating a change in configuration of aconnection towards the second base station;

receiving a message from the mobile terminal, the message indicatingthat the change in configuration is complete;

sending a parameter change acknowledgement to the second base station,in response to the message.

3. A method, in a second base station, for managing connectivity of amobile terminal to a first base station and the second base station, themethod comprising:

sending, to the first base station, radio resource configurationinformation for a connection between the mobile terminal and the secondbase station;

receiving a random access preamble from the mobile terminal, responsiveto the radio resource configuration information;

sending a random access response to the mobile terminal; and

receiving a parameter change acknowledgement from the first basestation.

It will be appreciated that other example embodiments include variationsof and extensions to these enumerated methods, in accordance with thedetailed procedures and variants described above.

In the above-description of various embodiments of present inventiveconcepts, it is to be understood that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of present inventive concepts. Unless otherwisedefined, all terms (including technical and scientific terms) usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which present inventive concepts belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of this specification andthe relevant art and will not be interpreted in an idealized or overlyformal sense expressly so defined herein.

When an element is referred to as being “connected”, “coupled”,“responsive”, or variants thereof to another element, it can be directlyconnected, coupled, or responsive to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected”, “directly coupled”, “directly responsive”,or variants thereof to another element, there are no interveningelements present. Like numbers refer to like elements throughout.Furthermore, “coupled”, “connected”, “responsive”, or variants thereofas used herein may include wirelessly coupled, connected, or responsive.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Well-known functions or constructions may not be described indetail for brevity and/or clarity. The term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that although the terms first, second, third, etc.may be used herein to describe various elements/operations, theseelements/operations should not be limited by these terms. These termsare only used to distinguish one element/operation from anotherelement/operation. Thus a first element/operation in some embodimentscould be termed a second element/operation in other embodiments withoutdeparting from the teachings of present inventive concepts. The samereference numerals or the same reference designators denote the same orsimilar elements throughout the specification.

As used herein, the terms “comprise”, “comprising”, “comprises”,“include”, “including”, “includes”, “have”, “has”, “having”, or variantsthereof are open-ended, and include one or more stated features,integers, elements, steps, components or functions but does not precludethe presence or addition of one or more other features, integers,elements, steps, components, functions or groups thereof. Furthermore,as used herein, the common abbreviation “e.g.”, which derives from theLatin phrase “exempli gratia,” may be used to introduce or specify ageneral example or examples of a previously mentioned item, and is notintended to be limiting of such item. The common abbreviation “i.e.”,which derives from the Latin phrase “id est,” may be used to specify aparticular item from a more general recitation.

Example embodiments are described herein with reference to blockdiagrams and/or flowchart illustrations of computer-implemented methods,apparatus (systems and/or devices) and/or computer program products. Itis understood that a block of the block diagrams and/or flowchartillustrations, and combinations of blocks in the block diagrams and/orflowchart illustrations, can be implemented by computer programinstructions that are performed by one or more computer circuits. Thesecomputer program instructions may be provided to a processor circuit ofa general purpose computer circuit, special purpose computer circuit,and/or other programmable data processing circuit to produce a machine,such that the instructions, which execute via the processor of thecomputer and/or other programmable data processing apparatus, transformand control transistors, values stored in memory locations, and otherhardware components within such circuitry to implement thefunctions/acts specified in the block diagrams and/or flowchart block orblocks, and thereby create means (functionality) and/or structure forimplementing the functions/acts specified in the Nock diagrams and/orflowchart block(s).

These computer program instructions may also be stored in a tangiblecomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks. Accordingly, embodiments of present inventiveconcepts may be embodied in hardware and/or in software (includingfirmware, resident software, micro-code, etc.) that runs on a processorsuch as a digital signal processor, which may collectively be referredto as “circuitry,” “a module” or variants thereof.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Finally, other blocks maybe added/inserted between the blocks that are illustrated, and/orblocks/operations may be omitted without departing from the scope ofinventive concepts. Moreover, although some of the diagrams includearrows on communication paths to show a primary direction ofcommunication, it is to be understood that communication may occur inthe opposite direction to the depicted arrows.

Many variations and modifications can be made to the embodiments withoutsubstantially departing from the principles of the present inventiveconcepts. All such variations and modifications are intended to beincluded herein within the scope of present inventive concepts.Accordingly, the above disclosed subject matter is to be consideredillustrative, and not restrictive, and the appended examples ofembodiments are intended to cover all such modifications, enhancements,and other embodiments, which fall within the spirit and scope of presentinventive concepts. Thus, to the maximum extent allowed by law, thescope of present inventive concepts are to be determined by the broadestpermissible interpretation of the present disclosure, and shall not berestricted or limited by the foregoing detailed description.

ABBREVIATIONS

3GPP 3rd Generation Partnership Project AMBR Aggregate Maximum Bit RateARP Allocation and Retention Priority BCH Broadcast Channel CIO CellIndividual Offset CN Core Network CRS Cell specific Reference Symbol DLDownlink DRB Data Radio Bearer E-UTRAN Evolved UMTS Terrestrial RadioAccess Network eNB/eNodeB enhanced Node B(base station) EPC EvolvedPacket Core EPS Evolved Packet System GBR Guaranteed Bit Rate HARQHybrid Automatic Repeat reQuest HeNB Home eNB IE Information Element LTELong Term Evolution MAC Medium Access Control MBR Maximum Bit Rate MMEMobility Management Entity MTCP Multi-path Transmission Control ProtocolNAS Non-Access Stratum P-GW PDN Gateway PCI Physical Cell Identity PDCPPacket Data Convergence Protocol PDN Packet Data Network PDU Packet DataUnit PSS Primary Synchronization Signal QCI QoS Class Identifier QoSQuality of Service RLC Radio Link Control RAB Radio Access Bearer REResource Element RRC Radio Resource Control RRH Remote Radio Head RRMRadio Resource Management RS Reference Signal RSCP Received Signal CodePower RSRP Reference Signal Received Power RSRQ Reference SignalReceived Quality S-GW Serving Gateway SDF Service Data Flow SDU ServiceData Unit SRB Signaling Radio Bearer SSS Secondary SynchronizationSignal TTT Time To Trigger UE User Equipment UL Uplink

The invention claimed is:
 1. A method performed in a wireless device forhandling connectivity to two network nodes, the method comprising:receiving, from a first network node, a radio resource configurationmessage, the radio resource configuration message indicating a change inconfiguration of a connection towards a second network node; applyingthe change in configuration towards the second network node in responseto the radio resource configuration message; and initiating a contentionbased random access procedure towards the second network node responsiveto applying the change in configuration, while maintaining connectivitywith the first network node, wherein said initiating comprises:transmitting a random access preamble; receiving a random accessresponse comprising a random access code from the second network node;and transmitting, to the second network node, a message comprising anidentifier of the wireless device, the identifier comprising a CellRadio Network Temporary Identifier (C-RNTI) assigned by the secondnetwork node.
 2. The method of claim 1, comprising sending a message tothe first network node, the message indicating that the change inconfiguration is completed.
 3. The method of claim 1, comprisingreceiving, from the first network node, a message comprising informationfor initiating the contention based random access procedure towards thesecond network node.
 4. The method of claim 3, wherein the informationcomprises a dedicated random access preamble or an identifier of thewireless device or both for the second network node.
 5. The method ofclaim 3, wherein the information is included in the radio resourceconfiguration message.
 6. The method of claim 1, wherein the randomaccess preamble is randomly selected.
 7. The method of claim 1,comprising receiving, from the second network node, a contentionresolution message.
 8. The method of claim 1, wherein the contentionbased random access procedure indicates that the change in configurationtowards the second node is complete.
 9. A wireless device for handlingconnectivity to two network nodes, the wireless device comprising atransmitter; a receiver; and a processor configured to: receive, via thereceiver, from a first network node, a radio resource configurationmessage, the radio resource configuration message indicating a change inconfiguration of a connection towards a second network node; apply thechange in configuration towards the second network node in response tothe radio resource configuration message; and initiate a contentionbased random access procedure towards the second network node responsiveto applying the change in configuration, while maintaining connectivitywith the first network node, by transmitting, via the transmitter, arandom access preamble; receiving, via the receiver, a random accessresponse comprising a random access code from the second network node;and transmitting, via the transmitter, to the second network node, amessage comprising an identifier of the wireless device, the identifiercomprising a Cell Radio Network Temporary Identifier (C-RNTI) assignedby the second network node.
 10. The wireless device of claim 9, whereinthe processor is further configured to send a message, via thetransmitter, to the first network node, the message indicating that thechange in configuration is completed.
 11. The wireless device of claim9, wherein the processor is further configured to receive, via thereceiver, from the first network node, a message comprising informationfor initiating the contention based random access procedure towards thesecond network node.
 12. The wireless device of claim 11, wherein theinformation comprises a dedicated random access preamble or anidentifier of the wireless device or both for the second network node.13. The wireless device of claim 9, wherein the processor is furtherconfigured to randomly select the random access preamble.
 14. Thewireless device of claim 9, wherein the processor is further configuredto receive, via the receiver, a contention resolution message from thesecond network node.
 15. The method of claim 9, wherein the contentionbased random access procedure indicates that the change in configurationtowards the second node is complete.
 16. A non-transitorycomputer-readable medium comprising, stored thereupon, a computerprogram for a wireless device for handling connectivity to two networknodes, the computer program comprising computer program code configuredso that, when the computer program code is executed on at least oneprocessor on the wireless device, the computer program code causes thewireless device to: receive, from a first network node, a radio resourceconfiguration message, the radio resource configuration messageindicating a change in configuration of a connection towards a secondnetwork node; apply the change in configuration towards the secondnetwork node in response to the radio resource configuration message;and initiate a contention based random access procedure towards thesecond network node responsive to applying the change in configuration,while maintaining connectivity with the first network node, saidinitiation comprising: transmitting a random access preamble; receivinga random access response comprising a random access code from the secondnetwork node; and transmitting, to the second network node, a messagecomprising an identifier of the wireless device, the identifiercomprising a Cell Radio Network Temporary Identifier (C-RNTI) assignedby the second network node.
 17. A method performed in a first networknode, for managing connectivity of a wireless device to the firstnetwork node and a second network node, the method comprising:receiving, from the second network node, radio resource configurationinformation for a connection between the wireless device and the secondnetwork node, the radio configuration information comprising anidentifier for the wireless device, the identifier including a CellRadio Network Temporary Identifier (C-RNTI); sending in response to andbased on the radio resource configuration information received from thesecond network node, a radio resource configuration message to thewireless device, the radio resource configuration message indicating achange in configuration of a connection towards the second network nodeand including the identifier for the wireless device; transmitting, tothe second network node, in response to the reception of the radioresource configuration information received from the second networknode, information about a contention based random access procedure to beinvoked by the wireless device; and receiving a message from thewireless device, the message indicating that the change in configurationis complete.
 18. The method of claim 17, comprising: sending a parameterchange acknowledgement to the second network node, in response to themessage indicating that the change in configuration is complete.
 19. Themethod of claim 17, wherein the contention based random access procedureto be invoked is between the wireless device and the first network node.20. A first network node for managing connectivity of a wireless deviceto the first network node and a second network node, the first networknode comprising a network interface; a radio transceiver; and aprocessor configured to: receive, via the network interface, from thesecond network node, radio resource configuration information for aconnection between the wireless device and the second network node, theradio configuration information comprising an identifier for thewireless device, the identifier including a Cell Radio Network TemporaryIdentifier (C-RNTI); send, via the radio transceiver, in response to andbased on the radio resource configuration information received from thesecond network node, a radio resource configuration message to thewireless device, the radio resource configuration message indicating achange in configuration of a connection towards the second network nodeand including the identifier for the wireless device; transmit, via thenetwork interface, to the second network node, in response to thereception of the radio resource configuration information, informationabout a contention based random access procedure to be invoked by thewireless device; and receive, via the radio transceiver, a message fromthe wireless device, the message indicating that the change inconfiguration is complete.
 21. The first network node of claim 20,configured to: send, via the network interface, a parameter changeacknowledgement to the second network node, in response to the messageindicating that the change in configuration is complete.
 22. The firstnetwork node of claim 20, wherein the contention based random accessprocedure to be invoked is between the wireless device and the firstnetwork node.
 23. A non-transitory computer-readable medium comprising,stored thereupon, a computer program for a first network node formanaging connectivity of a wireless device to the first network node anda second network node, the computer program comprising computer programcode configured so that, when the computer program code is executed onat least one processor on the first network node, the computer programcode causes the first network node to: receive, from the second networknode, radio resource configuration information for a connection betweenthe wireless device and the second network node, the radio configurationinformation comprising an identifier for the wireless device, theidentifier including a Cell Radio Network Temporary Identifier (C-RNTI);send, in response to and based on the radio resource configurationinformation received from the second network node, a radio resourceconfiguration message to the wireless device, the radio resourceconfiguration message indicating a change in configuration of aconnection towards the second network node and including the identifierfor the wireless device; transmit, to the second network node, inresponse to the reception of the radio resource configurationinformation received from the second network node, information about acontention based random access procedure to be invoked by the wirelessdevice; and receive a message from the wireless device, the messageindicating that the change in configuration is complete.
 24. A methodperformed in a second network node, for managing connectivity of awireless device to a first network node and the second network node, themethod comprising: sending, to the first network node, radio resourceconfiguration information for a connection between the wireless deviceand the second network node; receiving a random access preamble from thewireless device, wherein the random access preamble indicates that thewireless device has applied the radio resource configurationinformation; sending, responsive to the reception of the random accesspreamble, a random access response to the wireless device; andreceiving, from the wireless device, a message comprising an identifierof the wireless device, the identifier comprising a Cell Radio NetworkTemporary Identifier (C-RNTI) assigned by the second network node. 25.The method of claim 24, comprising receiving a parameter changeacknowledgement from the first network node.
 26. The method of claim 24,wherein the radio resource configuration information includes theidentifier of the wireless device.
 27. A second network node formanaging connectivity of a wireless device to a first network node andthe second network node, the second network node comprising a networkinterface; a radio transceiver; and a processor configured to: send, viathe network interface, to the first network node, radio resourceconfiguration information for a connection between the wireless deviceand the second network node; receive, via the radio transceiver, arandom access preamble from the wireless device, wherein the randomaccess preamble indicates that the wireless device has applied the radioresource configuration information; send, via the radio transceiver,responsive to the reception of the random access preamble, a randomaccess response to the wireless device; and receive, via the radiotransceiver, a message from the wireless device, the message comprisingan identifier of the wireless device, the identifier comprising a CellRadio Network Temporary Identifier (C-RNTI) assigned by the secondnetwork node.
 28. The second network node of claim 27, wherein theprocessor is further configured to receive, via the network interface, aparameter change acknowledgement from the first network node.
 29. Thesecond network node of claim 27, wherein the radio resourceconfiguration information includes the identifier of the wirelessdevice.
 30. A non-transitory computer-readable medium comprising, storedthereupon, a computer program for a second network node for managingconnectivity of a wireless device to a first network node and the secondnetwork node, the computer program comprising computer program codeconfigured so that, when the computer program code is executed on atleast one processor on the second network node, the computer programcode causes the second network node to: send, to the first network node,radio resource configuration information for a connection between thewireless device and the second network node; receive a random accesspreamble from the wireless device, wherein the random access preambleindicates that the wireless device has applied the radio resourceconfiguration information; send, responsive to the reception of therandom access preamble, a random access response to the wireless device;and receive a message from the wireless device, the message comprisingan identifier of the wireless device, the identifier comprising a CellRadio Network Temporary Identifier (C-RNTI) assigned by the secondnetwork node.
 31. A wireless device for handling connectivity to twonetwork nodes, the wireless device comprising a processor and a memorystoring instructions that, when executed by the processor, causes thewireless device to: receive, from a first network node, a radio resourceconfiguration message, the radio resource configuration messageindicating a change in configuration of a connection towards a secondnetwork node, apply the change in configuration towards the secondnetwork node in response to the radio resource configuration message,and initiate a contention based random access procedure towards thesecond network node responsive to applying the change in configuration,while maintaining connectivity with the first network node, saidinitiation comprising: transmitting a random access preamble; receivinga random access response comprising a random access code from the secondnetwork node; and transmitting, to the second network node, a messagecomprising an identifier of the wireless device, the identifiercomprising a Cell Radio Network Temporary Identifier (C-RNTI) assignedby the second network node.
 32. The wireless device of claim 31, whereinthe memory further stores instructions that, when executed by theprocessor, cause the wireless device to send a message to the firstnetwork node, the message indicating that the change in configuration iscompleted.
 33. The wireless device of claim 31, wherein the memoryfurther stores instructions that, when executed by the processor, causethe wireless device to receive, from the first network node, a messagecomprising information for initiating the contention based random accessprocedure towards the second network node.
 34. The wireless device ofclaim 33, wherein the information comprises a dedicated random accesspreamble or an identifier of the wireless device or both for the secondnetwork node.
 35. The wireless device of claim 33, wherein theinformation is included in the radio resource configuration message. 36.The wireless device of claim 31, wherein the memory stores instructionsthat, when executed by the processor, cause the wireless device torandomly select the random access preamble.
 37. The wireless device ofclaim 31, wherein the memory further stores instructions that, whenexecuted by the processor, cause the wireless device to receive, fromthe second network node, a contention resolution message.
 38. A firstnetwork node for managing connectivity of a wireless device to the firstnetwork node and a second network node, the first network nodecomprising a processor; and a memory storing instructions that, whenexecuted by the processor, cause the first network node to: receive,from the second network node, radio resource configuration informationfor a connection between the wireless device and the second networknode, the radio configuration information comprising an identifier forthe wireless device, the identifier including a Cell Radio NetworkTemporary Identifier (C-RNTI); send, in response to and based on theradio resource configuration information received from the secondnetwork node, a radio resource configuration message to the wirelessdevice, the radio resource configuration message indicating a change inconfiguration of a connection towards the second network node andincluding the identifier for the wireless device; transmit, to thesecond network node, in response to the reception of the radio resourceconfiguration information received from the second network node,information about a contention based random access procedure to beinvoked by the wireless device; and receive a message from the wirelessdevice, the message indicating that the change in configuration iscomplete.
 39. A second network node for managing connectivity of awireless device to a first network node and the second network node, thesecond network node comprising a processor; and a memory storinginstructions that, when executed by the processor, causes the secondnetwork node to: send, to the first network node, radio resourceconfiguration information for a connection between the wireless deviceand the second network node; receive a random access preamble from thewireless device, wherein the random access preamble indicates that thewireless device has applied the radio resource configurationinformation; send, responsive to the reception of the random accesspreamble, a random access response to the wireless device; and receive amessage from the wireless device, the message comprising an identifierof the wireless device, the identifier comprising a Cell Radio NetworkTemporary Identifier (C-RNTI) assigned by the second network node.